In an ion beam apparatus (hereinafter typified by an ion implantation apparatus), such as an ion implantation apparatus, parallelism of an ion beam has hitherto been performed in order to make an incident angle of the ion beam uniform within a plane of a target (e.g., a semiconductor substrate).
In order to prevent implantation, into the target, of ions of undesired energy (which will be referred to as “energy pollutants” or “energy contaminants”) (such implantation is called “energy pollution” or “energy contamination”) along with ions of desired energy, the ions of undesired energy are removed (this process is called “energy separation” or “energy analysis”).
Parallelism of the ion beam and energy separation have hitherto been performed through use of different functional elements.
Therefore, the length of the beam line of the ion beam has become longer, which in turn increases a loss due to divergence of the ion beam or a like cause. As a result, a drop occurs in the transport efficiency of the ion beam, thereby resulting in difficulty in ensuring a sufficient quantity of a beam. Particularly, the space-charge effect of the ion beam has noticeably appeared in transport of the ion beam at low energy, thereby diverging the ion beam and posing difficulty in efficient transport of the ion beam. Therefore, an ion implantation apparatus capable of shortening the length of the beam line as much as possible is desired.
Specific examples of the related art will now be mentioned. Japanese Patent Gazette No. 3-233845 (an area ranging from a right column on page. 1 to an upper left column on page. 2, FIG. 6) (hereinafter referred as Patent Document 1) describes a technique for separating energy through electrostatic deflection. However, an electrostatic deflection electrode used for energy separation is an electrode of parallel plate type, and the ion beam is not paralleled by the electrostatic deflection electrode. Parallelism of the ion beam is performed by another scanning electrode of parallel plate type provided for only parallelism purpose. Accordingly, as mentioned previously, there still arises a problem of an increase in the length of the beam line.
Another energy separation technique is to place a deflection electromagnet (at a downstream position) after the ion beam has been accelerated to final energy and to determine a turning radius R1 of the ion beam through use of the following equation. Here, “B” designates a flux density; “m” designates the mass of ions constituting an ion beam; “q” designates electric charges; and “V1” designates an accelerated voltage of the ion beam, which corresponds to energy.R1=(1/B)×(2 mV1/q)1/2  [Equation 1]
Such a technique is described as, e.g., an energy analysis magnet in Japanese Patent No. 33358336 (paragraphs 0002, 0003, FIG. 1) (hereinafter referred as Patent Document 2). However, the technique is practiced for an ion beam which is not subjected to scanning and parallelism. Parallelism of an ion beam is carried out through use of a deflection electromagnet which is provided for only parallelism purpose and is called another beam paralleling magnet. Accordingly, as mentioned previously, there still arises a problem of an increase in the length of the beam line.
A technique for performing parallelism of an ion beam scanned and energy separation through use of a single element (a sector-shaped electromagnet) is described in Japanese Patent Gazette No. 11-354064 (paragraphs 0016 to 0018, FIG. 1) (hereinafter referred as Patent Document 3).
The technique described in Patent Document 3 is for performing parallelism of an ion beam and energy separation through use of a deflection electromagnet called a sector-shaped electromagnet. In the case where the energy of the ion beam (corresponding to V1 in Equation 1) and the mass “m” of desired ions are increased, as can be seen from Equation 1, when an attempt is made to extract indium (In) ions having energy of 200 keV or more, a flux density B must be made extremely large in order to achieve a constant turning radius R1. For this reason, an iron core and a coil, which together constitute the deflection electromagnet, become very large, and hence the deflection electromagnet becomes huge. Moreover, there is also another problem of an increase in the weight and cost of the deflection electromagnet and the size of the power source for the deflection electromagnet or the like.
Moreover, the technique described in Patent Document 3 suffers the following problem. Namely, the ion beam is deflected by the deflection electromagnet within a plane in which a scanner called as an electrostatic deflector performs scanning of the ion beam. Therefore, if a deflection angle of the ion beam in the deflection electromagnet is not made very large, energy separation will not be performed sufficiently, which will in turn result in a failure to sufficiently eliminate ions of undesired energy. The reason for this is as follows. Both the ion beam having desired energy and ions having undesired energy have been spread after having been scanned by the scanner. In order to separate the thus-spread ion beams from each other within a single plane, the deflection angles of the ion beams must be made extremely large in comparison with a case where ion beams with narrow width are separated from each other or a case where the ion beams are separated from each other within different planes. Rendering the deflection angles extremely large corresponds to an extreme decrease in the turning radius R1 by means of rendering the flux density B expressed by Equation 1 very large. In such a case, a problem analogous to that described previously is still encountered.
If an attempt is made to solve the problem of incidence of ions of undesired energy onto a target without a substantial increase in the deflection angle of the deflection electromagnet, a distance from the exit of the deflection electromagnet to the target must be made longer. As a result, there is raised a problem of an increase in the length of the beam line.
Moreover, neutral particles—which are present as a result of molecules remaining in an atmosphere having collided with the ion beam—travel rectilinearly within the deflection electromagnet in, above, and below the deflection electromagnet. Unless the deflection angle of the deflection electromagnet is increased or unless the distance from the deflection electromagnet to the target is increased, the rectilinearly-traveling neutral particles is injected into the target. As a result, non-uniform implantation of the ions into the target has arisen. In order to solve the problem, there must be selected at least one from an option for rendering the deflection angle of the deflection electromagnet large and an option for increasing the distance from the exit of the deflection electromagnet to the target. In any event, there still remains a problem of an increase in the length of the beam line.